| Description: | The formation of vascular tissue occurs when cellulose, hemicellulose, lignin and other wall components are deposited within the primary cell wall. These secondary thickened cells then undergo programmed cell death producing a network of empty cells with which water and ions can be transported throughout the plant. The hormones auxin and cytokinin are the principle signals for vascular tissue initiation. As a consequence cells cultured in-vitro can be converted into vascular tissue with the addition of exogenous auxin and cytokinin.We have created an in-vitro cell system, using callus produced from leaves that can be induced to form vascular tissue. Leaves are callused on induction media for two weeks. The callus is then transferred to liquid media and incubated under optimum conditions resulting in an increase in vascular tissue formation. Approximately 20% of cells will differentiate during the incubation period. The alteration of cytokinin concentration affects the ability of the cultured cells to undergo differentiation. Consequently callus incubated in liquid media, containing lower cytokinin concentrations, will undertake relatively little differentiation. Samples have been isolated from cell cultures at different time points and different hormone concentrations during incubation. Quantitative PCR using the marker AtCesA7, which encodes a cellulose synthase subunit specific to secondary wall deposition, was used as a guide to determine periods of high and low vascular differentiation. This system provides an opportunity to compare gene expression between differentiating and non differentiating cells and allow the identification of genes up regulated during vascular tissue formation. |
NASCArrays Information at The BAR
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